Working steam produced upon incinerating the combustible wastes is mainly employed to a thermal power plant installed in an incineration plant. The thermal power plant, however, comes to a small-scaled facility which reduces a thermic efficiency gained upon converting a heat generation to an electricity. This makes it difficult to produce a thermal power plant to such a degree as applicable to a commercial and business usage.
For the thermal power plant installed in the incineration plant to generate the electricity due to the steam produced when the combustible wastes are incinerated, it is difficult to efficiently use the heat energy produced by the steam.
In the usual incineration plant, the quantity of the combustible wastes to be incinerated is regulated only to produce a comparably small quantity of the heat generation. In addition, the combustible wastes fluctuate in its quality and quantity on the daily basis, and the incineration plant is usually such treated as to suppress an emission of dioxin (polychlorinatd dibenzo-para-dioxin). For the fear that a incinerator furnace of the incineration plant would be damaged when inappropriate chemical products such as vinyl and plastic materials are thrown, it comes necessary to tentatively stop the operation upon checking or repairing the incineration plant.
Among the recently built thermal power plants employed for the commercial and business usage, there has been one in which a reheating-and-regenerating type Rankine cycle is utilized with super-critically high pressure, or a thermal power plant using a combined cycle in which the Rankine cycle is incorporated into a turbine. The thermic efficiency gained upon converting a thermal energy into an electricity in the former plant goes as high as approx. 42%, and the similar efficiency gained in the latter plant reaches 48%.
The thermic efficiency of the thermal power plant installed in the ordinary incineration plant is as low as approx. 10% on average, i.e., less than one-fourth of the above thermal power stations.
With this im mind, techniques have been sought out to make better use of a large quantity of the thermal energy of the steam and hot water generated when burning the combustible wastes in the incineration plant.
By way of illustration, FIG. 3 shows the thermal power plant with the super-critically high pressure in which the Rankine cycle is incorporated into the ordinary thermal power plant for commercial and business usage. This is based on a technological book (on page 44 of “Performance and Economy of Steam Turbine” written by Robert L. Bartlet and translated into Japanese by Eiichi Ishibashi and Yusaku Shibata, and published in 1965 by Ohm Corporation).
In the thermal power plant with the super-critically high pressure shown in FIG. 3, numeral 1 a super-critically high pressure boiler, 2 a steam-water mixed fluid, 3 a superheater, 4 a main steam, 5 a high pressure turbine, 6 a high pressure exhaust, 7 a reheater, 8 a reheating steam, 9 a medium pressure turbine, 10 a low pressure turbine, 11 an electric generator, 12 a low pressure exhaust, 13 a condenser unit, 14 a condensed water, 15 a condensed-water pump, 16 a low pressure feed water heater, 17 a low pressure bleed, 18-1 a low temperature feed water, 18-2 a medium temperature feed water, 18-3 a high temperature feed water, 19 a feed water pump, 20 a medium pressure feed water heater, 21 a medium pressure bleed, 22 a high pressure feed water heater, 23 a high pressure bleed, 24 a boiler feed water, 25 a drain water and 26 a drain pump.
The low pressure exhaust 12 released from the low pressure turbine 10 forms the condensed water 14 at the condenser unit 13 to transfer the condensed water 14 to the low pressure feed water heater 16 by means of the condensed-water pump 15, and heated by the low pressure bleed 17 extracted from the low pressure turbine 10 to result in the low temperature feed water 18-1 within the low pressure feed water heater 16.
The low temperature feed water 18-1 is transferred to the medium pressure feed water heater 20 by means of the feed water pump 19, and heated by the medium pressure bleed 21 extracted from the medium pressure turbine 9 to result in the medium temperature feed water 18-2 within the medium pressure water heater 20.
The medium temperature feed water 18-2 is transferred to the high pressure feed water heater 22, and heated by the high pressure bleed 23 extracted from the high pressure turbine 5 to result in the high temperature feed water 18-3 (boiler feed water 24) which is returned to the super-critically high pressure boiler 1.
Quantitative factors regarding the thermic efficiency gained upon converting the thermal generation to the electricity (referred sometimes merely to as “thermic efficiency” hereinafter) are improved in the following manner.
In the thermal power plant (700 MW class) with the super-critically high pressure, the steam-water mixed fluid 2 has a pressure of 26.5 MPa at a temperature of 375° C. The high pressure exhaust 6 has a pressure of 6.0 MPa at a temperature of 350° C. The low pressure exhaust 12 has a pressure of 0.005 MPa at a temperature of 28° C. The condensed water 14 has a pressure of 1.0 MPa at a temperature of 30° C. The main steam 4 has a super-critically high pressure of 24.6 MPa at a temperature of 538° C. The reheating steam 8 has a pressure of 4.4 MPa at a temperature of 593° C.
As quantitative factors regarding the regenerating cycle, the condensed water 14 has a pressure of 1.0 MPa at a temperature of 30° C. The boiler feed water 24 has a pressure of 29.5 MPa at a temperature of 300° C.
An incremental difference between an enthalpy of the boiler feed water 24 and that of the condensed water 14 is considered to be a total sum of the low pressure bleed 17 in the low pressure feed water heater 16, the medium pressure bleed 21 in the medium pressure feed water heater 20 and the high pressure bleed 23 in the high pressure feed water heater 22, including a pressure rise component in the feed water pump 19.
In the above thermal power plant realized by using the Rankine cycle, in order to elevate the enthalpy level of the condensed water 14 flowed out of the condenser unit 13 to the enthalpy level of the boiler feed water 24, it is necessary to install the low pressure feed water heater 16, the medium pressure feed water heater 20 and the high pressure feed water heater 22 (heater sources) to thermally heat the condensed water 14, the low temperature feed water 18-1, the medium temperature feed water 18-2 and the high temperature feed water 18-3.
Because the low pressure bleed 17, the medium pressure bleed 21 and the high pressure bleed 23 work as the heater sources for the condensed water 14 and the feed water to suppress an ineffective calorific heat from being generated, these pressure bleeds 17, 21 and 23 are very important factors to achieve the high thermic efficiency upon generating the electricity (refer to page 23 of the “Performance and Economy of Steam Turbine” as cited hereinbefore).
The following are individual factors shown for the purpose of comparing the thermal power plant to the large incineration plant.
(thermal power plant)
construction: thermal power plant used with super-critically high pressure (700 MW class),
fuel or combustible material used: coal,
power generation: 700 MW,
calorific heat quantity on average: 27,300 J/kg,
incineration or combustible quantity: 270 t/h,
main steam pressure: 24.5 MPa,
reheating steam pressure: 4.0 MPa,
main steam temperature: 566° C.,
reheating steam temperature: 596° C.,
condensed-water vacuum: 0.005 MPa,
thermic efficiency gained upon converting thermal generation to electricity: 42%,
reheating-and-regenerating cycle: adopted,
(large incineration plant)
construction; 504 t/day,
fuel or combustible material used: combustible wastes,
power generation: 27 MW,
calorific heat quantity on average: 4,800 J/kg,
incineration or combustible quantity: 62.5 t/h (19.2 t/h in terms of coal),
main steam pressure: 2.84 MPa,
reheating steam pressure: - - - ,
main steam temperature: 300° C.,
reheating steam temperature; - - - ,
condensed-water vacuum: 0.02 MPa,
thermic efficiency gained upon converting thermal generation to electricity: 11%,
reheating-and-regenerating cycle: not-adopted,
The large incineration plant belongs to a large-scaled accommodation facility in which each of three incinerator furnaces has an incineration capacity of 21 t/h to incinerate the combustible wastes at a rate of 504 t/day. The thermal power plant in the large incineration plant does not use the reheating-and-regenerating type Rankine cycle with the main steam pressure (2.84 MPa), the main steam temperature (300° C.) and the thermic efficiency (11%) as raised above. This evidently shows that the large incineration plant is inferior to the thermal power plant in any respective factors.
In the thermal power plant, the thermic efficiency reaches approx. 42%, and the same efficiency reaches as high as approx. 48% at the combined cycle in which the gas turbine is incorporated into the thermal power plant with super-critically high steam pressure.
Even in the thermal power plant efficiently equipped with the combined cycle, it makes the gas turbine and the reheating-and-regenerating type Rankine cycle as a basic combination. This requires the heater source as ever in order to elevate the enthalpy level of the condensed water to that of the boiler feed water 24.
The thermal energy based on the steam produced by the large incineration plant is supplied to the thermal power plant annexed to the large incineration plant, the thermic efficiency is, however, extremely inferior to that of the thermal power plant built for commercial and business purpose. For this reason, it has been highly expected to make an effective use of the thermal energy based on the steam generated by the large incineration plant.
The primary object of the invention is to provide a thermal power plant using a reheating-and-regenerating type Rankine cycle which is capable of making better use of a high temperature fluid produced upon incinerating a huge amount of combustible wastes at a large incineration plant.
The secondary object of the invention is to provide a thermal power plant using a reheating-and-regenerating type Rankine cycle which is capable of supplying the thermal energy to the reheating-and-regenerating type Rankine cycle (generated by the large incineration plant) without reducing the thermic efficiency gained upon converting the thermal energy to electric generation in the thermal power plant.
The tertiary object of the invention is to provide a thermal power plant using a reheating-and-regenerating type Rankine cycle which is capable of controlling a high temperature fluid (generated by the large incineration plant) from accidentally being fed into a water feed line of the thermal power plant.